Invasive Urban Mammalian Predators: Distribution and Multi-Scale Habitat Selection

Distribution dynamics and urbanization-related factors of Hantaan and Seoul virus infections in China between 2001 and 2020: A machine learning modelling analysis

Objectives

The epidemical and clinical features of distinct hantavirus infections exhibit heterogeneity. However, the evolving epidemics and distinct determines of the two hantavirus infections remain uncertain.

Methods

Data on hemorrhagic fever with renal syndrome (HFRS) cases and genotyping were collected from multiple sources to explore the distribution dynamics of different endemic categories. Four modelling algorithms were used to examine the relationship between infected hantavirus genotypes in HFRS patients, as well as assess the impacts of urbanization-related factors on HFRS incidence.

Results

The number of cities dominated by Hantaan (HTNV) and Seoul (SEOV) viruses was projected to decrease between two phases, while the mixed endemic cities increased. Patients with SEOV infection predominantly presented gastrointestinal symptoms. The modeling analysis revealed that built-up land and real GDP demonstrated the highest contribution to HTNV and SEOV infections, respectively. The impact of nightlight index and park green land was more pronounced in HTNV-dominant cities, while cropland, impervious surface, and floor space of commercialized buildings sold contributed more to HFRS incidence in SEOV-dominant cities.

Conclusions

Our findings fill a gap for the three endemic categories of HFRS, which may guide the development of targeted prevention and control measures under the conditions of urbanization development.

Waste reduction decreases rat activity from peri-urban environment

Globally, species in the genus Rattus (specifically Rattus rattus and Rattus norvegicus), are some of the most influential invasive taxa due to their high rates of competitive exclusion and large dietary breadth. However, the specific foraging strategies of urban-adjacent populations remain largely unknown. We examined Rattus spp. dependency on human food supplementation in a population on adjacent non-developed (or peri-urban) land. Via linear regression modeling, we measured rodent activity changes between native and invasive species before and after a decrease in human supplementation due to the COVID-19 lockdown in Santa Cruz, California, USA. We documented invasive rat activity via camera traps in normal (pre-COVID lockdown) conditions near dining halls and similar waste sources, and again under COVID lockdown conditions when sources of human supplementation were drastically decreased. After 120 trap nights we found a significant decrease (p < 0.001) in Rattus activity after the removal of human refuse, while native small mammal activity remained unchanged (p = 0.1). These results have strong conservation implications, as they support the hypothesis that proper waste management is an effective, less-invasive form of population control over conventional rodenticides.

Eradicating an invasive mammal requires local elimination and reduced reinvasion from an urban source population

Invasive mammal eradications are increasingly attempted across large, complex landscapes. Sequentially controlled management zones can be at risk of reinvasion from adjacent uncontrolled areas, and managers must weigh the relative benefits of ensuring complete elimination from a zone or minimizing reinvasion risk. This is complicated in urban areas, where habitat heterogeneity and a lack of baseline ecological knowledge increase uncertainty. We applied a spatial agent-based model to predict the reinvasion of a well-studied species, the brushtail possum (Trichosurus vulpecula), across an urban area onto a peninsula that is the site of an elimination campaign in Aotearoa New Zealand. We represented fine-scale urban habitat heterogeneity in a land cover layer and tested management scenarios that varied four factors: the density of possums remaining following an elimination attempt, the maintenance trap density on the peninsula, and effort expended toward preventing reinvasion by means of a high-density trap buffer at the peninsula isthmus or control of the source population adjacent to the peninsula. We found that achieving complete elimination on the peninsula was crucial to avoid rapid repopulation. The urban isthmus was predicted to act as a landscape barrier and restrict immigration onto the peninsula, but reliance on this barrier alone would fail to prevent repopulation. In combination, complete elimination, buffer zone, and source population control could reduce the probability of possum repopulation to near zero. Our findings support urban landscape barriers as one tool for sequential invasive mammal elimination but reaffirm that novel methods to expose residual individuals to control will be necessary to secure elimination in management zones. Work to characterize the urban ecology of many invasive mammals is still needed.

Rodent management in Aotearoa New Zealand: approaches and challenges to landscape-scale control

Aotearoa-New Zealand has only four rodent species, all introduced. In order of arrival, they are Pacific rat Rattus exulans, brown rat R. norvegicus, house mouse Mus musculus, and black rat R. rattus. Rodent management in New Zealand aims mainly to conserve indigenous biodiversity rather than to protect crops or manage diseases, as is usual elsewhere. We describe four major "regimes" and one major vision for rodent control in New Zealand to meet ecological restoration objectives. Current challenges for island eradications are for large islands that are remote or populated by people. Aerial 1080 is the only large-scale (tens of thousands of hectares) option for black rat control, but its application requires adjustment to counter subsequent rapid black rat repopulation. Unfenced "ecosanctuaries" (mean 720 ha) use ground-based traps and poisons to target mainly black rats and face constant reinvasion. Ecosanctuaries with mammal-resistant fences (up to 3500 ha) limit reinvasion and target more pest species and have enabled the return of previously extirpated taxa to the main islands. Predator Free 2050 aims to eradicate the rat species (but not mice) plus some other introduced mammals from New Zealand by 2050. This vision is not attainable with current tools, but research and experimental management is exploring techniques and technologies. The large scale (to 100 000 ha) at which black rats are now targeted for control to extremely low abundance seems to be unique to New Zealand.

Climate match is key to predict range expansion of the world's worst invasive terrestrial vertebrates

Understanding the determinants of the range expansion of invasive alien species is crucial for developing effective prevention and control strategies. Nevertheless, we still lack a global picture of the potential factors influencing the invaded range expansion across taxonomic groups, especially for the world's worst invaders with high ecological and economic impacts. Here, by extensively collecting data on 363 distributional ranges of 19 of world's worst invasive terrestrial vertebrates across 135 invaded administrative jurisdictions, we observed remarkable variations in the range expansion across species and taxonomic groups. After controlling for taxonomic and geographic pseudoreplicates, model averaging analyses based on generalized additive mixed-effect models showed that species in invaded regions having climates more similar to those of their native ranges tended to undergo a larger range expansion. In addition, as proxies of propagule pressure and human-assisted transportation, the number of introduction events and the road network density were also important predictors facilitating the range expansion. Further variance partitioning analyses validated the predominant role of climate match in explaining the range expansion. Our study demonstrated that regions with similar climates to their native ranges could still be prioritized to prevent the spread of invasive species under the sustained global change.